Subject to the application, sensors tend to be integrated on semiconductor substrates. This kind of manufacturing is beneficial in that the size of the sensors can significantly be reduced compared to discrete type sensors, and such sensors can be arranged next to electronic circuitry integrated on the same semiconductor substrate which circuitry may include functions acting on a signal delivered by the sensor such as amplification, evaluation, etc.
An integrated chip comprising a sensor is called sensor chip in the following. In such sensor chip, the sensor and possibly electronic circuitry are arranged at a front side of a substrate. The circuitry may be formed by CMOS processing, and the building and/or arranging of a sensing element of the sensor on the front side may be implemented in a way compatible to CMOS processing. When such sensor chip needs to be integrated into a processing system, the sensor chip typically will be connected to circuitry residing on a different circuit board, such as a printed circuit board, for example. A preferred way for mounting a sensor chip to such circuit board is a technique called flip chip mounting in which the sensor chip is flipped such that its front side containing the sensing element and the circuitry faces the circuit board and is electrically connected to it. The electrical connection typically is achieved between contact pads arranged at the front side of the sensor chip and contact pads arranged on the circuit board and solder material in between.
However, now the sensing element faces the circuit board which may not be preferred for various reasons: In case the sensor shall detect a quantity of a measure in the environment of the sensor, such measure may not have sufficient access to the sensing element for the reason of its arrangement facing the circuit board. And even if there is sufficient access granted to the medium to be measured, it may not be appreciated that such medium also gets in touch with the circuit board. In case, for example, the medium to be measured is a gas, such gas may damage the circuitry on the circuit board.
For solving the above problem, a technique called through-silicon vias may be applied. Such vias are arranged in the semiconductor substrate and represent vertical electrical connections between the front side of the substrate and its back side. A sensor chip with through-silicon vias can be mounted on the circuit board with its back side facing the circuit board and with its front side including the sensing element facing away from the circuit board. Contact pads arranged at the back side of the sensor chip allow electrically contacting the circuit board.
However, the handling of such sensor chip appears to be difficult in that both sides of the chip, i.e. the front side and the back side contain exposed elements such as the sensing element and the contact pads.